1. Field of the Invention
The present invention relates to an apparatus and a process for air-blown gasification of carbon-containing fuels involving heat exchange between endothermic and exothermic reactions.
2. Discussion of Background
For the gasification of coal or residue oil, use is currently made primarily of oxygen-blown processes, for example the Shell carbon gasification process. These processes produce a gas having a relatively high calorific value, 12-15 MJ/kg, which, owing to its low mass flow rates, can be desulfurized without large enthalpy loss and dedusted using washing devices. In this case the typical gasification reactions EQU CH4+H2O.fwdarw.CO+3HT (1) EQU C+H2O.fwdarw.CO+H2 (2)
proceed endothermically.
The required energy is, for example, provided by exothermic reaction EQU 2C+O2.fwdarw.2CO (3a)
In this case, approximately 22% of the calorific value of the fuel is converted by the exothermic reaction (3a) first in two sheets and then, via the endothermic reactions (1) and (2) back into fuel enthalpy.
In the case of an air-blown gasification process according to the prior art, the exothermic reaction (3a) would become: EQU 2C+O2+4N2.fwdarw.2CO+4N2 (3b)
and the calorific value of the product gases is reduced to less than 50% in comparison with oxygen-blown gasification.
An essential disadvantage of this process is the fact that the gasification product is contaminated with atmospheric nitrogen.